Children do benefit from the intellectual environment created at home—and for children who grow up with their biological families, that environment tends to be an expression or an amplification of their genes. As I described earlier, smart families are likely to create smart environments. This is not only true for parents. Developmental psychologist Sandra Scarr followed adopted children as they grew up and found that children create their own environments—she called it "niche picking." Imagine two children within a family who seem, from day one, to be really different. One child, Emmanuel, learns to talk at an early age and loves words. It is clear almost immediately that he is attuned to the conversations around him and quick to use new vocabulary, try out verbal expressions, and tell stories.

Intelligence: As Smart As the Day You Were Born

His brother, Dwight, seems more visual right from the beginning. Whenever he can, he uses toys to make patterns, buildings, and other visual displays. He seems to notice details in whatever room he enters. Even if Emmanuel and Dwight share the same parents and the same bedroom, go to the same family celebrations, attend the same nursery school, and spend their weekends on the same playground, they will experience substantively different environments. While Emmanuel listens to his parents' conversation, sits in rapt attention while his uncle tells a story, and creates elaborate stories when he is with his playmates, Dwight is oblivious to the conversation, spending his time instead taking all of the silverware and making a giant pattern with it, watching his grandfather repair the cabinet, and making patterns with colored blocks. These two children are, in effect, creating their own intellectual environment. Whatever it was they were born with, in terms of cognitive ability and style, leads them to notice, seek out, and immerse themselves in particular facets of the world around them. Emmanuel will grow up in a more language-rich environment than Dwight, who, in contrast, will grow up in a more visually rich environment than his brother.

Understanding what makes up a child's intelligence does not require parsing out the genetic component and the environmental component. Genes only express themselves within a particular environment. You can't be smart without questions, tools, and people to be smart with. But the questions, tools, and people you pick up on are shaped, in part, by your intelligence. Especially in the case of children who are raised by their biological parents, the IQs they get through their genes are often merely amplified by the IQs that surround them in their homes. The smart mom who has a large vocabulary provides her child not only with her genes but also with the kind of language-rich environment that enhances her child's native capacity.

Sign of Intelligence

What does this all mean for your child? To begin with, it means that your child's intelligence is likely to be similar to yours (and by the way, most research shows that people are likely to marry someone of similar intelligence, so you needn't fret too much about whether your child will get your wonderful IQ or your mate's lowly IQ).